1. Field of the Invention
The present invention relates to a projector type vehicle headlamp, particularly relates to a vehicle headlamp constituted to be able to irradiate an overhead sign (traffic sign).
2. Related Art
Generally, a vehicle headlamp of a projector type is constituted to reflect light from a light source arranged on an optical axis extended in a front and rear direction of a vehicle to a front side to be proximate to an optical axis by a reflector, and irradiate reflected light thereof to a front side of a lamp device by way of a projector lens provided on a front side of a reflector.
Further, when the vehicle headlamp of the projector type is constituted for irradiating a low beam (passing beam), the beam is irradiated to the front side by a low beam light distribution pattern having a predetermined cutoff line by providing a shade for removing irradiating light in an upward direction by blocking a portion of reflected light from a reflector between a projector lens and the reflector.
According to the headlamp of the projector type, the irradiating light in the upward direction is substantially completely removed by the shade, and therefore, an overhead sign (OHS) placed on an upper side of a road on a front side of a vehicle is not well seen.
Hence, in a background art, there is proposed a vehicle headlamp in which an opening portion is formed at a portion of a vicinity of an upper end edge of the shade, a rear face of the shade is provided with a light blocking plate in a shape of an eaves extended to a skewed lower side from between the upper end edge and the opening portion to a rear side. A portion of reflected light in an upward direction reflected by a lower reflecting region of the reflector is made to be incident on a projector lens by way of the opening portion to thereby provide overhead sign irradiating light for irradiating an overhead sign (refer to, for example, JP-A-2003-297117).
However, a light distribution pattern by the overhead sign irradiating light of JP-A-2003-297117 is determined by a contour shape of the opening portion formed at the portion at the vicinity of the upper end edge of the shade, the opening portion per se cannot adjust an intensity of transmitted light. Therefore, it is difficult to adjust an illuminance distribution at inside of the light distribution pattern. Particularly, it is extremely difficult to partially reduce an illuminance of a portion of a region at inside of the light distribution pattern even when a fine work is introduced to the shape of the opening portion.
Therefore, when there is brought about a request for forming a dark portion having an illuminance lower than that of a surrounding thereof of a portion in the light distribution pattern by the overhead sign irradiating light from, for example, a countermeasure against glare of a vehicle running on an opposed lane or laws or regulations or the like, it is difficult to deal therewith.